Gliederung

Introduction

One of the main postulated basic principles of total disc replacement (TDR) is the preservation of flexion/extension ability. In neutral position the ideal disc prosthesis should not stay in maximal possible extension which would imply an impingement of the prosthesis. An impingement can cause shear strains on the prosthesis endplates which probably accelerate loosening. The purpose of study was to evaluate a possible impingement after TDR.

Material

In 29 patients with a mean age of 42.4 Â± 6.5 years the segmental lordosis and flexion/extension ability was measured after single-level disc replacement with the Prodisc IIÂ® . The follow up interval averaged 13.2 months.

Methods

Pre- and postoperative lateral X-rays in neutral position, in maximum flexion and extension were assesed. The angulation of prosthesis in neutral position and the extension ability on dynamic x-rays were measured with the Cobb-Method.

Results

15 patients showed no extension ability on dynamic x-rays and 10 of these 15 patients had an impingement with maximum extension of the prosthesis on x-rays in neutral position. In the remaining 14 patients the extension ability averaged pre-/postoperatively 2.3Â°/1.3Â° (p=0.115). In 4 of the 14 patients the prosthesis showed an impingement in maximum extension and in 10 patients the prosthesis was not in maximum possible extension.

Conclusion

An impingement was recognized in nearly 30% of the cases after implantation of the ProDisc. It still remains unclear if an impingement will result in facet joint protection or will trigger a loosening of the implant.